In existing monochrome passive matrix OLED (PMOLED) display applications, it is desirable to display, at least for a short period of time, grayscale patterns or images for better visual effect; for example, showing a logo during the device startup. It is not known that there is any existing display driver that has built-in mechanism that provides the aforesaid function. There are, however, commercially available standalone grayscale image display driver or module to provide such function in monochrome PMOLED displays. In general, grayscale image display driver has embedded full size memory and more hardware than monochrome driver. Once grayscale image is stored in the embedded memory, greyscale driver can generate grayscale image itself without extra external control. On the other hand, the working principle of monochrome image display drivers and modules is that display image data is written into the display driver for every frame and the frame-rate-control (FRC) is varied to produce the grayscale image. This involves complex control between the host controller and the display driver, such as signal timing synchronization for preventing tearing effects.